| Maxwell Thomas Limited | Real estate | 2002 |
| Maya Dufeu Ltd | Information & communication | 2024 |
| Maya, Inc. Kids Ltd | Arts & recreation | 2022 |
| Mayals Management Limited | Information & communication | 2000 |
| Mayb Holdings Limited | Financial services | 2023 |
| Mayes Design Ltd | Information & communication | 2021 |
| Mayfair Roofing Limited | Construction | 2018 |
| Mayfield Motors (Sussex) LLP | | 2004 |
| Maysy Limited | Information & communication | 2017 |
| Maytree Residents Limited | Households | 2019 |
| Mayvin Limited | Professional & scientific | 2010 |
| Mazoe Properties Limited | Real estate | 2009 |
| MB Landscapes (Sussex) Limited | Administrative & support | 2017 |
| MB Writer Limited | Extraterritorial | 2007 |
| Mbls Language Services Limited | Professional & scientific | 2014 |
| Mbodha Limited | Professional & scientific | 2022 |
| Mbrv Ltd | Professional & scientific | 2025 |
| MC Compliance Limited | Professional & scientific | 2025 |
| MC Martin Contractors Ltd | Manufacturing | 2016 |
| MC3 Design Hove Limited | Other services | 2018 |
| Mcalfie Developments Ltd | Real estate | 2024 |
| Mcbeth Creative Limited | Arts & recreation | 2012 |
| Mccallum Family Holdings Ltd | Financial services | 2025 |
| Mccanns Launderettes Limited | Other services | 2006 |
| Mccanns Property Limited | Real estate | 2025 |
| Mccreath Financial Partners Limited | Financial services | 2011 |
| Mcguinness Hall Consultants Ltd | Professional & scientific | 2018 |
| Mckenna Civil Engineering Limited | Construction | 2018 |
| Mckenzie Shaw Limited | Professional & scientific | 2021 |
| Mckeown Estates Ltd | Construction | 2024 |
| Mclennan Dale Ltd | Construction | 2024 |
| MCN Productions Ltd | Information & communication | 2011 |
| Mcnally Property Limited | Real estate | 1995 |
| Mcphail Career Development Ltd | Education | 2017 |
| MD Essentials Ltd | Wholesale & retail | 2025 |
| Mdjc Ltd | Wholesale & retail | 2026 |
| MDM Hove Ltd | Hospitality | 2019 |
| MDM Property Holdings Limited | Real estate | 2019 |
| MDS Dent Limited | Health & social care | 2022 |
| Mdtea Limited | Wholesale & retail | 2012 |
| MDU Foods Ltd | Hospitality | 2023 |
| ME Security Ltd | Real estate | 2022 |
| Meadows Brothers Enterprises Ltd | Wholesale & retail | 2022 |
| Meadows Media Limited | Information & communication | 2015 |
| Meaningful Care Matters Ltd | Professional & scientific | 2019 |
| Meaningful Paths Ltd | Other services | 2020 |
| Meatdown Limited | Real estate | 1986 |
| Mechanics of YOU Ltd | Information & communication | 2022 |
| Mechial Properties Ltd | Financial services | 2024 |
| Med-Doc Ltd | Health & social care | 2025 |
| Medhurst Heating & Plumbing Limited | Construction | 2002 |
| Medi Brighton Ltd | Hospitality | 2020 |
| Media Betty Limited | Information & communication | 2005 |
| Media Content Limited | Professional & scientific | 2019 |
| Media South Advertising Ltd | Information & communication | 2011 |
| Media Trend Ltd | Information & communication | 2012 |
| Medical Beauty Aesthetics Company Ltd | Other services | 2025 |
| Medical Organisation for the Needy Ltd | Health & social care | 2025 |
| Medical Solutions Group Limited | Financial services | 2016 |
| Medicine Woman Ltd | Manufacturing | 2018 |
| Medigenes Ltd | Professional & scientific | 2022 |
| Medina RTM Company Limited | Real estate | 2014 |
| Medina Villas Freehold (Hove) Limited | Households | 2019 |
| Meditate Records Limited | Arts & recreation | 2018 |
| Meds Barber Ltd | Other services | 2021 |
| Meemanda Rose Homecare Limited | Health & social care | 2015 |
| Meena Allen Ltd | Administrative & support | 2015 |
| Meercat Consulting Limited | Professional & scientific | 2003 |
| Meerkat Works Limited | Professional & scientific | 2005 |
| Mega Maintenance Limited | Administrative & support | 2007 |
| Mega Never DIE Ltd | Information & communication | 2025 |
| Mehmet & SON Building Services Ltd | Construction | 2019 |
| Meikle Investments Ltd | Real estate | 2011 |
| Melina Enterprises Limited | | 1983 |
| Mellish Homes Ltd | Administrative & support | 2009 |
| Melora Holdings Ltd | Financial services | 2023 |
| Meloy Architecture & Design Ltd | Professional & scientific | 2022 |
| Melville 6 Limited | Households | 2010 |
| Melvinshaw Limited | Real estate | 2017 |
| MEN Dream Property Limited | Construction | 2021 |
| Mendip Solar Ltd | Energy | 2012 |
| Mens Pocket Squares Ltd | Wholesale & retail | 2016 |
| Menstethics Ltd | Health & social care | 2025 |
| Mental IDE Ltd | Professional & scientific | 2010 |
| Meoko Limited | Information & communication | 2021 |
| Meowtron Ltd | Information & communication | 2024 |
| Meraki Dental Aesthetics Limited | Health & social care | 2019 |
| Meraki Digital Ltd | Wholesale & retail | 2025 |
| Mercadinho Ltd | Wholesale & retail | 2022 |
| Merge Coffee & Bakes Ltd | Manufacturing | 2026 |
| Meridian Management & Property Ltd | Hospitality | 2026 |
| Meridian Operating Partners Ltd | Professional & scientific | 2026 |
| Merturi Lettings Limited | Real estate | 2018 |
| Meshhopper Wi-Fi Networks Limited | Manufacturing | 2003 |
| Messagemedia Europe Limited | Information & communication | 1999 |
| Messina Finance Limited | Real estate | 2009 |
| Messina Holdings Limited | Real estate | 2009 |
| Messina Investments Limited | | 2025 |
| Messina Investments Limited | Financial services | 2002 |
| Messina Properties Limited | Real estate | 2009 |